I’ve been short-listed for two categories in the Association of British Science Writers awards: feature, and communication of science in a non-science context. Dead chuffed. Also the latter category is in memory of Stephen White, who taught the 2-day course that convinced me I wanted to be a science writer. It’s an honour.

Second, I am really excited by this RNA world result, so thanks for the tip on the Nature blog article!

The reason is because it coincides with the recent phylogeny of Braakman and Smith on evolution of metabolism, which according to them shows sign of divergence precisely after the creation of the oxygen atmosphere.* The pre-LUCA would have been fitted with a curiously robust, redundant and over evolutionary time stable metabolic network that were fixed by “imprecise or unreliable enzyme function … or unreliable regulation”.

They point out that this would leave open the possibility of chemical evolution at early stages, but it could as well be used to signal a disappearing RNA world. (Smith is working specifically on chemical evolution, IIRC.) [“The Emergence and Early Evolution of Biological Carbon-Fixation”, Braakman and Smith, PLoS Comp Biol, 2012.]

That Benner sees precisely the implication that the change from RNA to protein catalysis can be tied to the time of oxygenation is promising. More specifically, it would be the point where an eventual mixture of catalysts would latest see the RNA mostly replaced. It is an excellent bottleneck constraint explaining why RNA world life disappeared in toto.**

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* This raises the question if not cyanobacteria were responsible for the atmospheric change, what was? A blog article at the time pointed to a paper where a presumed global glaciation at the time lead to the first UV-driven release of massive amounts of oxygen.

The initial pulses of the poisonous substance would have tipped the balance and eventually lead up to a diversity of oxygenating photosynthesizers. In effect reversing the usual oxygenating photosynthesis – oxygen – glaciation supposed order of events.

** Except possibly surviving as some parasitically simplified RNA viruses akin to what people believed happened to the putative DNA Megavirus ancestor.

Can anyone tell me why the tornadoes seem to follow a pronounced forward slash kind of pattern? I would have guessed (in my admitted ignorance regarding tornado physics) that it would be much more random.

Jenny Morber Says:Can anyone tell me why the tornadoes seem to follow a pronounced forward slash kind of pattern? I would have guessed (in my admitted ignorance regarding tornado physics) that it would be much more random.

I assume you’re referring to “west to east” paths? Weather in the US generally follows the jet stream, which generally flows east-to-west. The thunderstorm cells that birth tornadoes generally get carried along the jet stream. This is just a generalization, events like hurricanes can drive tornadoes in unusual directions. Generally.